Global Volcanism Program | Image GVP-04346
The unvegetated channel that descends diagonally from the right center to the lower left is the passageway of lahars in the upper Guali River drainage on the north flank of Nevado del Ruiz. Farm houses are visible on the opposite side of the channel for scale. The Río Guali lahars traveled more than 100 km from the volcano at velocities of about 5-15 meters/second.
Photo by Tom Pierson, 1985 (U.S. Geological Survey).